1. Field of the Invention
The present invention relates to an apparatus for scraping away substances adhering to the inner wall of a rotary kiln so as to perform the operation of the rotary kiln continuously for a long time and enhance the operation efficiency of the rotary kiln.
2. Description of the Prior Art
When rubbery or plastic materials or city garbage are thermally decomposed by using a rotary kiln or when coal is carbonized or various materials are dried in a rotary kiln, and other substances are accumulated on the inner wall of the rotary kiln to form a layer with the lapse of time and such layer has bad influences on the operation. Especially in case of a rotary kiln of the external heating type, transfer of heat through the wall of the rotary kiln is drastically inhibited by such layer of adhering substances and hence, the operation becomes impossible in a short time. Accordingly, in order to perform the operation continuously, it is necessary to remove substances adhering to the inner wall of the rotary kiln.
As the conventional apparatus for agitating a material to be treated in a rotary kiln and preventing the material from adhering to the inner wall of the rotary kiln, there can be mentioned apparatuses illustrated in the specifications of U.S. Pat. No. 3,245,154 and U.S. Pat. No. 3,333,837. In these conventional apparatuses, however, since the apparatuses per se are continuously rotated while the rotary kiln is being rotated, and since they fall in contact with the inner face of the rotary kiln only by virtue of their own weights, there are brought about various disadvantages. For example, slips are readily caused on the rotation of the apparatus with increase of the substances adhering to the inner wall of the rotary kiln or by the adhering force of the accumulated substances, and the apparatus rotates on the layer of the substances adhering to the inner wall of the rotary kiln and presses strongly the adhering substances to the inner wall of the rotary kiln. Accordingly, removal of the adhering substances cannot be accomplished at a high efficiency or completely, and therefore, the heat transfer efficiency is degraded in the rotary kiln.